Fluorocarbon resins such as polytetrafluoroethylene (PTFE) have excellent nonadhesiveness, heat resistance, and chemical resistance and thus are often used as materials constituting coatings of cookers such as rice cookers and cookware such as hot plates and frying pans and topcoat layers of fixing rollers for use in office automation equipment such as copiers. The reason fluorocarbon resins such as PTFE have excellent heat resistance and chemical resistance is that in a structural formula described below, the bonding strength between C and F is the highest among organic substances (116 kcal/mol) and that fluorine atoms (F) entirely cover carbon chains to protect the C—C bonds. The reason for the excellent nonadhesiveness is a very low polarization of charges because of the symmetry of the atomic arrangement in a molecule, a low cohesive force between molecules, and a significantly low surface energy.

Fluorocarbon resins have these excellent physical properties but disadvantageously have poor abrasion resistance. The reason for this is that molecules are readily detached because of a low surface energy and a low cohesive force between fluorine atoms (F—F).
To overcome this problem, currently commercially available fluorocarbon resins compensate the weakness by forming very long molecular chains having a degree of polymerization of about 10,000 to several hundred thousands, i.e., a molecular weight of about a million to tens of millions, to increase the bonding strength between fluorocarbon resins. However, it is difficult to achieve a higher molecular weight because of problems with formability and so forth (a reduction in flowability). Thus, sufficient properties are not provided. Furthermore, the adhesion of fluorocarbon resins to bases is a processing problem due to excellent nonadhesiveness. To solve this problem, in the case of using a base composed of a metal such as aluminum, it is necessary to conduct an additional step of performing etching treatment to form irregularities or forming an adhesive layer such as a primer.
In recent years, a technique in which a fluorocarbon resin, which is a representative of polymers degraded by electron beams, is crosslinked by electron beam irradiation at a temperature equal to or higher than the melting point thereof in an oxygen-free atmosphere has been developed (Patent Documents 1 and 2). It is found that to solve the problem in which the molecules are readily detached because of a low cohesive force between fluorine atoms (F—F), crosslinking a fluorocarbon resin results in a three-dimensional network structure of fluorine atoms as shown in a structural formula below, so that the polymeric chains are strongly bonded to each other, significantly improving the abrasion resistance.
    [Patent Document 1] Japanese Patent No. 3587071    [Patent Document 2] Japanese Patent No. 3587072